1. Field
Embodiments of the invention relate to the field of busses for very high speed digital signals; and more specifically, to providing a flexible arrangement of multiple high speed connectors.
2. Background
Modern digital systems are using interconnections to carry signals at increasingly high frequencies. For example, the High-Definition Multimedia Interface (HDMI) and the Digital Video Interface (DVI) use cables that carry signals at data rates of up to 3.4 Gbps.
The audiovisual (AV) data carried on these high speed channels is encoded by a technique called Transition Minimized Differential Signaling (TMDS). TMDS uses paired signal wires with a controlled differential impedance of 100Ω to maintain signal integrity. Because of the very high data rates, every aspect of the signal path must be carefully designed and built to exacting tolerances to maintain the differential impedance of the data paths.
In the HDMI/DVI standard, four differential pairs carry the TMDS signals. For DVI, three of these pairs are dedicated to carrying RGB video and sync data. For HDMI, audio data is also interleaved with the video data; the DVI standard does not incorporate audio information. The fourth high speed differential pair is used for the AV clock and runs at one-tenth the speed of the TMDS data channels.
To ensure interoperability of components using HDMI signaling, components are required to successfully pass compliance testing at an Authorized Testing Center (“ATC”) authorized by the HDMI Founders for testing products in accordance with the HDMI Compliance Test Specification prior to mass production or distribution if such product claims conformance to the High-Definition Multimedia Interfaces or bears any Adopted Trademark. Such compliance testing typically includes Display Data Channel (DDC) bus capacitance, TMDS line characteristic impedance, and consumer electronics control (CEC) bus capacitance.
HDMI components, such as video display devices, typically provide more than one HDMI connector to accommodate several sources of audiovisual content that may be selected for display. Components may be members of a family of devices that provide varying levels of capabilities while sharing a common core of basic functionality. The number of HDMI connectors provided may be such a variable capability.
It would be desirable to provide a system that allows a variable number of high speed connectors to be provided on a device without requiring that every configuration undergo time-consuming compliance testing. It would be desirable for such system to be inexpensive to manufacture.